Superfund sites have arisen in part because systems were developed for materials processing, energy production, manufacturing, and waste management without sufficient consideration of the health and environmental impacts of byproducts or waste from processes or product use and disposal. Combustion systems are used for the treatment and destruction of wastes, and dominate the production of energy and materials. In all these applications, they have the potential to produce air pollution and hazardous byproducts. Combustion processes are also the major source of ultrafine particles, especially those smaller than 1 micron. The long-range goals of this project are to improve high-temperature processes, particularly combustion processes, and to provide a means of on-line real time monitoring of air emissions. These efforts can contribute to the reduction of direct and indirect exposures to toxic combustion byproducts, especially to metals, chlorinated hydrocarbons (CHCs), and small particles. In the proposed research, we seek understanding of the processes and mechanisms that result in the evolution of particles and gas-phase seek understanding of the processes and mechanisms that result in the evolution of particles and gas-phase byproducts in high temperature environments. In addition, combustion may be regarded as a model system for applying environmental metrics during the design phase to improve performance and reduce environmental health impacts. One additional dimension of the project will be to extend the application of excimer laser fragmentation-fluorescence spectroscopy (ELFFS) to the measurement of toxic species in soils or solids; this work may provide additional resources to other program projects, which involve the fate and transport of toxic metals and CHCs in the ground. The specific aims for this project are: 1) Continue development of non- intrusive monitoring techniques (such as ELFFS and in situ Fourier transform infrared (FTIR) spectroscopy) for application to metals and other hazardous species produced in flames or in the post-flame environment. 2) Study the behavior of metals and metal species in flames and in the post-flame environment with the goal of identifying conditions that produce specific metal compounds and particles. 3) Expand our studies of the chemistry and interactions of chlorinate hydrocarbons to mixtures where chlorine, metals, and oxygenates are present. 4) Use the information generated in aims #2 and #3 combined with toxicity metrics to explore possible design and control strategies to reduce the amount and toxicity of species emitted to the environment when high temperature systems are utilized. 5) Extend our laser diagnostic methods to the detection of metals and metal compounds in solids and soils.